subshape,subshape_label,shape,shape_label
arrow,arrow,cospan,cospan
arrow,arrow,endomorphism,endomorphism
arrow,arrow,pair of parallel arrows,pair of parallel arrows
arrow,arrow,span,span
arrow,arrow,tower,tower
empty diagram,empty diagram,point,point
pair of points,pair of points,arrow,arrow
point,point,pair of points,pair of points
tower,tower,transfinite composition,transfinite composition